michael finney explains the run down. >> they keep us looking good. mail carriers get us mail rain or shine. sanitation workers do one of dirtiest jobs around. holidays a good time to show your appreciation with a tip. cindy is founder of advanced etd the question. >> tipping is mostly optional in most instances, as a result it's something more personal. >> the survey of 1800 americans found bar bergs receive an average tip of $10. teachers get an average $20. so do mail carriers and newspaper carriers, pet care providers and sanitation workers gardeners do better a ap at $25 and housekeepers get an average tip of $50. >> you tip what you have extra to spare and to share. >> i tip if i feel people give me a friendly good service and treat me kindly and don't make me feel like, i owe them something. >> she suggests another option. >> the difference is for people who serve you year round. i think a gift is much more personal than just giving money. >> not everyone agrees. they found 39% of those surveyed they didn't tip at all last holiday season. 55% o